1. Field of the Invention
This invention relates to laser devices, a laser system including the laser devices and an output mirror for the laser system. The invention is particularly concerned with improvements in laser devices each comprising: one or more axially symmetrical columnar laser media; one or more axially symmetrical columnar pump light sources arranged parallelly to each other and adjoining the laser media; and a beam converger having a reflective surface including two or more partially cylindrical curved surfaces and two or more partial plain surfaces arranged plane-parallelly, said curved surfaces and said plain surfaces plane-parallelly and substantially uniformly surrounding the laser media and the pump light sources in the axial direction thereof. Further, the invention relates to a laser system including the improved laser devices. The invention is concerned with an output mirror capable of being used in the common laser systems, in which a necessary optical component out of incident rays are transmitted and the transmitted light is reflected in a direction opposite of the incident rays.
2. Description of the Prior Art
The laser beams, differing from the common naturally emitted lights, have various characteristics such as the coherence and excellent monochromaticity. Because of these characteristics, the laser beams have been widely used of measuring with high accuracy and high sensitiveness, meteorology, study of nonlinear optics, optical communication and so forth.
FIG. 30 is an explanatory view showing the conventional structure of a laser system using the above-described laser beams. In this drawing, the laser oscillator is comprised of a laser device (a lamp house for the oscillator) 3, a total reflection mirror 5, and a half mirror 9 with a half-transmittable film 2. The laser beams emanated from the laser oscillator are successively reflected rectangularly by prisms 6a, 6b, 6c and 6d and led to a laser device (a lamp house for the amplifier) 4. Upon being amplified by the laser amplifier 4, the laser beams are reflected rectangularly by a prism 6e and thrown to a body to be measured, not shown, and the like. In place of the prisms 6a -6e, total reflection mirrors may be used. In this case, similarly to the prisms 6a -6e, the total reflection mirrors are arranged at positions where the beams are reflected rectangularly.
As the above-described laser devices 3 and 4, as disclosed in Walter Koechner: Solid-State Laser Engineering, pp301-306 (Springer Verlag, 1976) and Japanese Patent Unexamined Publication No. 51-40894 for example, these have been most widely used a device of the type in which a laser rod 12 and a pump lamp 11 are placed at two foci 41 and 42 of a beam converger 10 of an elliptic cylinder as shown in FIG. 31. In this arrangement, being based on the geometrical theorem, the beam converging property is high. In this type, the highest efficiency can be obtained when the laser rod 12 is placed with the pump lamp 11 in close proximity. Furthermore, in Japanese Patent Unexamined Publication No. 50-85291, there is disclosed one in which two pump lamps 11 and 13 are placed on both sides of the laser rod 12 as shown in FIG. 32, and another in which laser rods 12 and 14 are placed on both sides of the pump lamp 11 as shown in FIG. 33.
However, any way, the pump lamps 11, 13 and the laser rods 12, 14 are placed at the foci 41, 42, 43 and 44 of the ellipse, whereby the intensity of the light from the pump lamps becomes extremely high in the vicinity of the axes of the laser rods, thus presenting a problem that optical elements reach the limit of destruction when laser beams are oscillated or amplified and a high output energy cannot be obtained as the whole of beam. Further, there has been another problem that there occur portions of the laser rod to which the light of the pump lamp fails to reach, whereby the output as the whole of beam is decreased.
In order to solve the above mentioned two problems, in Japanese Patent Unexamined Publication No. 62-183193, there is disclosed a laser device in which the axis of the laser rod is shifted from the focal point of the elliptic cylinder. As shown in FIG. 34, in this laser device, the axis 31 of the pump lamp 11 is placed at one focus 41 of the beam converger 10 consisting of the elliptic cylinder and a point within the laser rod is placed at the other focus 42 and axis 32 of the laser rod 12 is shifted between the two foci 41 and 42.
According to this laser device, the distribution of light intensity from the laser rod is improved, however, the degree of uniformity of the distribution is not satisfactory, thus presenting a problem that merely the position of the highest intensity is shifted from the axis of the laser rod.
Furthermore, in the above-described literature by W. Koechner, there are disclosed laser devices of the type having beam convergers which do not form a focus such as a cross-section of a circle, arcs and straight-lines or an oval shape.
Out of the laser devices of this type, one in which the laser rod is placed to the pump lamp in close proximity provides easy fabrication and the distribution of the intensity of the laser is improved. However, it has a problem that the efficiency is low as compared with the laser device of the elliptic cylinder type. Further, the distribution of laser intensity is improved as compared with the elliptic cylinder type, however, it has a problem that the improvement is not satisfactory.
Further, in the above-described literature U.S. Pat. No. 4751716, there is disclosed a laser device of a multiple connection in which a plurality of pump lamps are provided. In the multiple connection type mentioned above is improved in the uniformity of laser intensity in the cross-section of the laser rod as compared with the case of the single pump lamp. However, it leads to a problem that the construction is complicated and large-sized, so that it is not suitable for some application.
The laser system as shown in FIG. 30 has further problems as follows.
Even if the outer dimension of the half mirror 9 in the laser system shown in FIG. 30 is 20 mm for example, the outer dimension of a mirror holder holding the half mirror 9 becomes as much as about 40-.dbd.mm. Because of this, in the case where the distance between an optical axis 7 of the laser oscillator 3 and an optical axis 8 of the laser amplifier 4 is as close as about 20-25 mm, there have been necessary the four prisms 6a -6d to pass the oscillated laser beams through the laser amplifier 4 as shown in FIG. 30.
Even when the distance between the optical axis 7 of the laser oscillator 3 and the optical axis 8 of the laser amplifier 4 is more than 25 mm, it has been necessary to provide the half mirror 9 and at least two total reflection mirrors (or one or two prisms).
Consequently, when the optical axes 7 and 8 are close to each other in particular, the number of optical elements such as the prisms 6a -6d is increased as shown in FIG. 30, thus presenting a problem that adjustment of optical axes of the respective optical elements becomes such complicated. In addition, when the number of optical elements is increased, a large space is needed to set and arrange these optical elements, thus presenting a problem that it is difficult to render the laser system compact in size.